1. Technical Field
The present invention relates to methods for recording, for example, images on recording media using a liquid such as ink.
2. Related Art
One widely known recording apparatus for recording on recording media using a liquid is an ink-jet recording apparatus that ejects ink onto recording paper (hereinafter simply referred to as the “recording apparatus”). This type of recording apparatus includes a transportation mechanism that transports recording paper in a transportation direction and a recording head that ejects ink onto the recording paper transported into the apparatus by the transportation mechanism. When the recording apparatus receives image data from a host computer connected to the recording apparatus, the recording head ejects various inks onto the recording paper to record an image based on the image data in a recording region of the recording paper.
The recording paper used for recording can expand or contract under the effect of, for example, the atmosphere where the recording apparatus is installed (particularly, humidity) and the ejected inks. In addition, the recording paper can be transported by the transportation mechanism while remaining inclined with respect to the transportation direction. In such cases, the recording head can fail to eject the inks at appropriate positions on the recording paper. To solve this problem, the following two methods have been proposed.
In a first method, upon completion of recording on a first sheet of recording paper, the spacing between an end of a recording region of the recording paper subjected to recording and an end of the recording paper (i.e., the margin spacing) is measured, and the difference between that spacing and a predetermined spacing set as a recording condition in advance is calculated. Subsequently, recording on second and subsequent sheets of recording paper is performed such that the pattern of ink ejection onto the recording paper is corrected on the basis of the above difference. This allows appropriate recording on recording paper even if the recording paper expands or contracts or is transported while remaining inclined (see JP-A-2004-142269).
A second method is to use recording paper on which a predetermined mark is formed at a recording starting position in advance. When such recording paper is transported into the apparatus, the mark is detected by a mark detector (such as a sensor) and is used as a reference for ink ejection. As a result, an appropriate image is recorded at an appropriate position on the recording paper (see JP-A-7-9728).
A line-head recording apparatus has recently been under development that includes a plurality of (e.g., two) recording units having a length greater than or equal to that of recording paper in its width direction and arranged at intervals in the transportation direction. Of these recording units, an upstream recording unit positioned upstream in the transportation direction is configured so that it can eject some types of inks (e.g., cyan ink and magenta ink), whereas a downstream recording unit positioned downstream in the transportation direction is configured so that it can eject other types of inks (e.g., yellow ink and black ink). In this recording apparatus, the upstream recording unit ejects some types of inks onto the recording paper before the downstream recording unit appropriately ejects other types of inks onto the recording paper so that they overlap the positions where the inks ejected from the upstream recording unit have landed.
During the recording, the inks ejected from the upstream recording unit onto the recording paper may locally expand the sites where the inks have landed on the recording paper. This may cause the landing positions of the inks ejected from the downstream recording unit onto the same sheet of recording paper to deviate from target positions with respect to the landing positions of the inks ejected from the upstream recording unit. Such misalignment between the landing positions of the inks ejected from the upstream recording unit and the landing positions of the inks ejected from the downstream recording unit results in irregularities in the image recorded on the recording paper. There is therefore room for improvement in the quality of the image recorded on the recording paper.